Physics Classes

23/09/2026

21/09/2026

IMP. MCQ ON ELECTRIC FIELD

21/09/2026

I got over 2,000 reactions on my posts last week! Thanks everyone for your support! 🎉

20/09/2026

TzRY TO ANSWER--

20/09/2026

With Innocent Shadrach Haiwulu – I just got recognized as one of their top fans! 🎉

19/09/2026

REFLECTING TYPE TELESCOPE

*Principle:* It uses *reflection* of light instead of refraction. Distant object rays are collected by a large concave mirror.

*Construction:*
1. *Concave Primary Mirror (M1):* Large parabolic mirror at bottom of tube. Acts as objective. Aperture is large.
2. *Secondary Mirror (M2):* Small convex mirror near focal point.
3. *Eyepiece:* Convex lens at side of tube.

*Working:*
1. Parallel rays from distant star/planet enter telescope tube.
2. Primary concave mirror reflects and converges them to its focal point (F).
3. Before forming image at F, a small 45° plane mirror intercepts the beam and reflects it 90° towards side.
4. This reflected beam enters eyepiece, which magnifies and forms final enlarged virtual image at infinity.
*Advantages over Refracting Telescope (IMPORTANT for 2 marks):*

- *No Chromatic Aberration:* Mirror reflects all colours equally, no dispersion.
- *No Spherical Aberration:* Parabolic mirror used.
- *High Brightness:* Large aperture mirror collects more light, can see faint stars.
- *Cheap:* Making large mirror is cheaper than large lens.
- *Light weight:* Mirror is lighter than lens of same power.

This is why *all big telescopes* (Keck, Hubble, James Webb) are reflecting type.